A section of a device is shown in FIG. 1 to illustrate a general method for forming a gate electrode.
A polysilicon film 4 for a gate electrode is formed on a silicon substrate 1 formed with a field oxide film 2 and a gate oxide film 3. A photoresist pattern 9 is formed on the top of the polysilicon film 4 by means of a lithography process utilizing a gate electrode mask. The gate electrode is formed by a polysilicon etching process using the photoresist pattern 9 as an etching mask. However, as the semiconductor device is highly integrated, the gate electrode becomes small in its pattern line width. The pattern line width of the gate electrode is determined by the photoresist pattern. In order to form a pattern line width of the gate electrode equal to or smaller than that of the critical dimensions therefor, a highly developed lithography process is required and an expensive exposing apparatus is necessary to form the photoresist pattern used as the etching mask.